Usually you get about an hour or two notice. A lot of people who go the fake pee leave a bottle in their car with heat pads so they are ready to go.

For trades jobs, how much you get tested is a bit of a crapshoot. The big construction unions usually require random testing (IBEW definitely). Beyond that, the place you work for a project might require pre-site tests and randoms. Anything in chemical industry, utilities, or oil and gas definitely will, and it's hair testing so you have to abstain completely. Other stuff, less likely.